1. Field of the Invention
The present invention relates to a device for damping torsional vibration of a drive shaft. More particularly, it relates to a device where planetary gears form a gear pump for closed circulation of a liquid damping medium.
2. The Prior Art
A device for damping torsional vibration is disclosed in DE 39 18 063 A1, which corresponds to U.S. Pat. No. 5,078,246. In the patented device, the planetary gears are spur gears which mesh with a central ring gear. The spur gears are devoid of an axial journal and are flatly supported between axial face plates in pockets of a planetary gear carrier.
The intake and pressure sides of the gear pumps are present at the radially outwardly disposed mesh point of the planetary gears and the central gear. Each pressure duct is provided with a storage chamber with an elastically changeable volume and is connected with the intake side of the next geared pump. A piston valve throttles each pressure duct. The valve is controlled based on the speed at which the main gear revolves. An excess pressure valve is also provided. Such design requires a large number of precisely made parts which results in higher manufacturing costs.